The epidermal growth factor receptor (EGFR, Erb-B1) belongs to a family of proteins, involved in the proliferation of normal and malignant cells (Arteaga, C. L., J. Clin. Oncol. 19, 2001, 32-40). Overexpression of Epidermal Growth Factor Receptor (EGFR) is present in at least 70% of human cancers (Seymour, L. K., Curr. Drug Targets 2, 2001, 117-133) such as, non-small cell lung carcinomas (NSCLC), breast cancers, gliomas, squamous cell carcinoma of the head and neck, and prostate cancer (Raymond et al., Drugs 60 Suppl. 1, 2000, discussion 41-2; Salomon et al., Crit. Rev. Oneal. Hematol. 19, 1995, 183-232; Voldborg et al., Ann. Oneal. 8, 1997, 1197-1206). The EGFR-TK is therefore widely recognized as an attractive target for the design and development of compounds that can specifically bind and inhibit the tyrosine kinase activity and its signal transduction pathway in cancer cells, and thus can serve as either diagnostic or therapeutic agents. For example, the EGFR tyrosine kinase (EGFR-TK) reversible inhibitor, TARCEVA®, is approved by the FDA for treatment of NSCLC and advanced pancreatic cancer. Other anti-EGFR targeted molecules have also been approved including LAPATINIB® and IRESSA®.
Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) are effective clinical therapies for EGFR mutant advanced non-small cell lung cancer (NSCLC) patients (Mok, T. S., et al., N. Engl. J. Med. 361, 2009, 947-57; Paez, J. G., et al., Science. 304, 2004, 1497-500; Lynch, T. J., et al., N. Engl. J Med. 350, 2004, 2129-39; Rosell, R., et al., Lancet Oncol. 13, 2012, 239-46). Several randomized clinical trials have demonstrated that EGFR TKIs are more effective, as measured by response rate (RR) and progression free survival (PFS), than chemotherapy when used as initial systemic treatment for advanced EGFR mutant NSCLC (Mok, T. S., et al., N. Engl. J. Med. 361, 2009, 947-57; Rosell, R., et al., Lancet Oncol. 13, 2012, 239-46; Sequist, L. V. et al., J. Clin. Oncol. 31, 2013, 3327-34; Wu, Y. L., et al., Lancet Oncol. 15, 2014, 213-22; Maemondo, M., et al. N. Engl. J. Med. 362, 2010, 2380-8; Zhou, C., et al., Lancet Oncol. 12, 2011, 735-42; Mitsudomi, T., et al., Lancet Oncol. 11, 2010, 121-8). However, the vast majority of patients will develop disease progression following successful treatment with an EGFR TKI. The most common mechanism of acquired resistance, detected in 60% of patients, is a secondary mutation in EGFR at position T790 (T790M) (Yu, H. A., et al., Clin. Cancer Res. 19, 2013, 2240-7). This mutation, leads to an increase in ATP affinity, thus making it more difficult for reversible EGFR TKIs gefitinib and erlotinib to bind the EGFR TKI domain (Yun C. H., et al., Proc. Natl. Acad. Sci. USA. 105, 2008, 2070-5).
Covalent EGFR inhibitors have emerged as strategies to inhibit EGFR T790M containing cancers. However, in lung cancer patients, afatinib is only effective in EGFR TKI naive EGFR mutant cancers and has a RR of <10% in patients with NSCLC that have developed resistance to gefitinib or erlotinib (Miller V. A., et al., Lancet Oncol. 13, 2012, 528-38). Afatinib is a potent inhibitor of both mutant and wild type (WT) EGFR. Inhibition of WT EGFR leads to toxicities, including skin rash and diarrhea, which limits the ability to escalate afatinib doses in patients to those necessary to inhibit EGFR T790M. Irreversible pyrimidine EGFR inhibitors, including the tool compound WZ4002 and clinical compounds CO-1686 and AZD9291, overcome many of the limitations of afatinib (Zhou, W., et al., Nature 462, 2009, 1070-4; Walter, A. O., et al., Cancer Discov. 3, 2013, 1404-15; Cross, D. A., et al., Cancer Discov. 2014). They are not only more potent on EGFR T790M, but also selectively inhibit mutant over WT EGFR and hence should lead to increased clinical efficacy and less toxicity compared with afatinib (Zhou, W., et al.; Walter, A. O., et al; Cross, D. A., et al.).
However, all current EGFR TKIs target the ATP site, and while third generation irreversible inhibitors can overcome T790M, they are all rendered impotent by the C797S mutation, which is already arising in treated patients. Cetuximab, an anti-EGFR antibody that blocks receptor dimerization is not effective in EGFR-mutant NSCLC, because mutational activation of the kinase is effectively “downstream” of receptor dimerization. Hence, alternative strategies to inhibit EGFR are needed. At present, suitable compounds with alternative mechanisms of action targeting mutant EGFR are not available. Thus, there is a need for novel and potent small molecule EGFR inhibitors with alternative mechanisms of action targeting mutant EGFR.